In a Long Term Evolution (Long Term Evolution, LTE) system, when uplink data needs to be transmitted, user equipment (User Equipment, UE) uses an uplink scheduling request (Scheduling Request, SR) mechanism. The UE sends an uplink scheduling request to a base station, and notifies the base station that the UE requires an uplink resource to transmit data. After receiving the scheduling request from the UE, the base station allocates some resources to the UE, and the UE transmits data on these allocated resources. However, this mechanism causes heavy signaling overheads.
To resolve the foregoing problem, a grant-free (Grant Free) technical solution has been provided. Grant free means that in a public land mobile network (Public Land Mobile Network, PLMN), UE does not need to request, by using a scheduling request, a base station to allocate a resource for data transmission. A grant-free user may directly use a grant-free transmission mode to transmit a packet on a contention transmission unit (contention transmission unit, CTU) according to different data transmission characteristics, such as requirements on a transmission delay or reliability.
Uplink grant free (Grant free) may reduce overheads and redundancy caused by frequent scheduling requests. On an uplink channel, instead of requesting a resource, a grant-free terminal directly uses a grant-free resource to perform uplink transmission.
An uplink grant-free transmission method based on a contention transmission unit (contention transmission unit) is provided in the prior art.
A terminal selects one CTU from one or more CTUs to send uplink data. However, if different terminals select a same code domain resource in a same CTU, a receive end cannot decode the data sent by the terminals. This reduces decoding reliability.